// Copyright 2018 gf Author(https://github.com/gogf/gf). All Rights Reserved.
//
// This Source Code Form is subject to the terms of the MIT License.
// If a copy of the MIT was not distributed with this file,
// You can obtain one at https://github.com/gogf/gf.

package gstr

// Soundex calculates the soundex key of a string.
// See http://php.net/manual/en/function.soundex.php.
func Soundex(str string) string {
    if str == "" {
        panic("str: cannot be an empty string")
    }
    table := [26]rune{
        '0', '1', '2', '3',           // A, B, C, D
        '0', '1', '2',                // E, F, G
        '0',                          // H
        '0', '2', '2', '4', '5', '5', // I, J, K, L, M, N
        '0', '1', '2', '6', '2', '3', // O, P, Q, R, S, T
        '0', '1',                     // U, V
        '0', '2',                     // W, X
        '0', '2',                     // Y, Z
    }
    last, code, small := -1, 0, 0
    sd := make([]rune, 4)
    // build soundex string
    for i := 0; i < len(str) && small < 4; i++ {
        // ToUpper
        char := str[i]
        if char < '\u007F' && 'a' <= char && char <= 'z' {
            code = int(char - 'a' + 'A')
        } else {
            code = int(char)
        }
        if code >= 'A' && code <= 'Z' {
            if small == 0 {
                sd[small] = rune(code)
                small++
                last = int(table[code-'A'])
            } else {
                code = int(table[code-'A'])
                if code != last {
                    if code != 0 {
                        sd[small] = rune(code)
                        small++
                    }
                    last = code
                }
            }
        }
    }
    // pad with "0"
    for ; small < 4; small++ {
        sd[small] = '0'
    }
    return string(sd)
}
